R/grocery.R

In pid: Process Improvement using Data

# (c) Kevin Dunn, 2018.

grocery <- function(P=3.46, H=150){
  # Simulates a grocery store profit function where there are 2 factors:
  #   P = selling price of the product, measured in dollars and cents
  #   H = height of the product on the shelf, measured in centimeters above the ground.
  #
  # Typical values for P = $3.50 and H = 150cm
  #
  # The outcome is: profit made per hour [dollars/hour].

  if ( (length(P) > 1) | (length(H) > 1)) {
    stop("Running the grocery store experiments in parallel is (intentionally) not allowed.")
  }
  if (!all(is.finite(P)) | !all(is.finite(H))) {
    stop("All function inputs must be finite numbers.")
  } else if (P < 0) {
    stop("Please provide a positive sales price, P.")
  } else if (H < 0) {
    stop("The height of the shelving, H, must be a positive value.")

  } else{
    a_coded <- (P - 3.2) / 0.2
    b_coded <- (H - 50) / 100
    y <- round( (18 * a_coded + 12 * b_coded - 7 * a_coded * a_coded
                 - 6.0 * b_coded * b_coded  - 8.5 * a_coded * b_coded + 60) * 10.0
                + rnorm(1) * 2 )
  }
  return(y)
}